BOSTON, Nov 15 (Reuters) - Engine No. 1"s head of active engagement Charlie Penner, who conceived and quarterbacked this year"s successful board challenge at Exxon Mobil Corp (XOM.N) that stunned the corporate world, is leaving the sustainability-focused hedge fund. Penner, a partner at Engine No. 1, has informed the firm that he is resigning, the company said, confirming a Reuters report based on information from two sources familiar with the decision. He plans to continue running activist campaigns while collaborating with other large investors. "We appreciate the tremendously valuable work Charlie put in at Engine No. 1, especially on the Exxon campaign, and we wish him well in his future endeavors," an Engine No. 1 spokesman said in a statement. Engine No. 1, which had only $250 million in assets when it opened for business less than a year ago, made a big splash in May when shareholders elected three of the four directors the hedge fund nominated to the U.S. oil company"s board. The hedge fund made an initial investment of $40 million and argued that Exxon, which is now valued at $270 billion, needed new blood in light of its poor financial performance and lack of a broad plan to address climate change. read more It spent $12.5 million on the campaign. Penner joined Engine No. 1 in October 2020 as a partner and brought the idea of battling Exxon to the fund. He ran the campaign with a team, selecting director nominees, speaking with Exxon"s board, and presenting the hedge fund"s case to top Exxon shareholders including Vanguard, BlackRock and State Street. He moved to the new firm, founded by Chris James, after 15 years at Barry Rosenstein"s activist firm Jana Partners. Other Engine No. 1 investments include Microsoft (MSFT.O), General Motors (GM.N) and Square Inc (SQ.N). In June the firm rolled out an exchange traded fund, betting that Main Street investors want portfolios to back environmental, social and governance proposals (ESG) on the heels of its Exxon win. Penner has worked on activist campaigns for more than a decade and is credited with having launched the first ever ESG focused activist campaign in 2018. Jana Partners pushed Apple to take steps to address the growing addiction of young people to its iPhones. Pension fund California State Teachers Retirement System (CalSTRS) backed both the Apple and Exxon campaigns. In 2019 Penner privately pressured McDonald"s Corp (MCD.N), also while cooperating with CalSTRS, to sell plant-based burgers in order to help address declining guest traffic, according to people familiar with the matter. Reporting by Svea Herbst-Bayliss in Boston; Editing by David Gregorio